Some of these parameters that may have a man-made component and a few ideas on how they could be measured are discussed below.


Net Radiation Budget All components of this can be measured accurately from space. To detect variations significant for climate, emphasis should be placed on stable instruments and vehicles with long useful lifetimes. Man contributes to the radiation budget by release of heat and by changing surface characteristics, topics treated elsewhere in this volume. These can be monitored to some extent from space. Although trivial in terms of energy, artificial light may be statistically related to total energy release with sufficient reliability to be a useful monitoring tool, since artificial light can be easily detected from space at night. This approach might provide a simple means for monitoring changes in human energy consumption patterns.


Surface Albedo Man changes surface albedo through deforestation, urbanization, grazing, agriculture, etc. These changes also affect evapotranspiration and surface roughness. All of these factors can be monitored by multispectral remote sensing.


Soil Moisture This can be roughly determined from space by passive microwave radiometry. Irrigation, agricultural practices, and large-scale hydrological works of man have significant impact on soil moisture, which in turn affects the albedo, surface temperature, and moisture flux relevant to climate. Both human activities and their consequences in terms of soil moisture should be monitored.


Water Runoff River flow statistics are sensitive indicators of climate variations over the continents and also are influenced by man-made changes in the land. It is difficult to acquire such data directly from space, but satellite communication may make feasible the collection of data from isolated locations.


Carbon Dioxide It is not possible to identify uniquely the contribution of man except by source monitoring and spectral analysis. Of particular value in carbon dioxide monitoring will be measurement of the vertical distribution on a global basis with a view to identification of sources, sinks, and transport mechanisms. This knowledge might clarify the roles of the land biota and the oceans in the atmospheric carbon cycle.


Ozone There is no significant contribution of ozone by man on a global scale. However, ozone is critical in the human environment because of its role in screening out damaging ultraviolet components of the solar system. Other trace gases can act as catalysts to reduce ozone concentration. It is therefore important to monitor this gas.


Tropospheric Aerosols These represent a mixture of natural and man-made particles and can be monitored from space. Some estimates of the proportion due to man may be possible by relating contrast changes due to aerosol loading with known patterns of human activities.


Atmospheric Turbidity This can be monitored through the depolarization of sunlight by aerosols [see, for example, page 208 of Remote Measurement of Pollution (NASA, 1971)]. It is also possible to monitor turbidity from the changes in apparent contrast of surface targets of known intrinsic contrast [McLlellan in NASA (1971)].


Stratospheric Aerosols Concern has been expressed on possible increases in stratospheric aerosols due to high-altitude aircraft operations, Limb-scanning techniques in the infrared can be used to search for features due to aerosols. Measurements of the solar disk and the aureole in two wavelengths can give both the real and the imaginary parts of the refractive index, together with particle size.


Trace Gases Limb scanning with an interferometer-spectrometer as done by Rudolf Hanel of the NASA Goddard Space Flight Center (personal communication) in planetary investigations can provide information.

REFERENCES

ICSU/WMO (1975). Report of the Eleventh Session of the Joint Organizing Committee, Tokyo, Oct. 1–8, 1975, Global Atmospheric Research Programme.

National Aeronautics and Space Administration (1971). Remote Measurement of Pollution, Scientific and Technical Information Office, NASA, Washington, D.C.

U.S. Committee for GARP (1975). Panel on Climatic Variation, Understanding Climatic Change: A Program for Action, National Academy of Sciences, Washington, D.C.

WMO/ICSU (1975). World Meteorological Organization and International Council of Scientific Unions, The Physical Basis of Climate and Climate Modelling, GARP Publ. Series No. 16, Geneva.



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